A previously uncharacterized two-component signaling system in uropathogenic Escherichia coli coordinates protection against host-derived oxidative stress with activation of hemolysin-mediated host cell pyroptosis

PLoS Pathog. 2021 Oct 15;17(10):e1010005. doi: 10.1371/journal.ppat.1010005. eCollection 2021 Oct.


Uropathogenic Escherichia coli (UPEC) deploy an array of virulence factors to successfully establish urinary tract infections. Hemolysin is a pore-forming toxin, and its expression correlates with the severity of UPEC infection. Two-component signaling systems (TCSs) are a major mechanism by which bacteria sense environmental cues and respond by initiating adaptive responses. Here, we began this study by characterizing a novel TCS (C3564/C3565, herein renamed orhK/orhR for oxidative resistance and hemolysis kinase/regulator) that is encoded on a UPEC pathogenicity island, using bioinformatic and biochemical approaches. A prevalence analysis indicates that orhK/orhR is highly associated with the UPEC pathotype, and it rarely occurs in other E. coli pathotypes tested. We then demonstrated that OrhK/OrhR directly activates the expression of a putative methionine sulfoxide reductase system (C3566/C3567) and hemolysin (HlyA) in response to host-derived hydrogen peroxide (H2O2) exposure. OrhK/OrhR increases UPEC resistance to H2O2 in vitro and survival in macrophages in cell culture via C3566/C3567. Additionally, OrhK/OrhR mediates hemolysin-induced renal epithelial cell and macrophage death via a pyroptosis pathway. Reducing intracellular H2O2 production by a chemical inhibitor impaired OrhK/OrhR-mediated activation of c3566-c3567 and hlyA. We also uncovered that UPEC links the two key virulence traits by cotranscribing the c3566-c3567 and hlyCABD operons. Taken together, our data suggest a paradigm in which a signal transduction system coordinates both bacterial pathogen defensive and offensive traits in the presence of host-derived signals; and this exquisite mechanism likely contributes to hemolysin-induced severe pathological outcomes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Escherichia coli Infections / metabolism
  • Escherichia coli Infections / pathology*
  • Hemolysin Proteins / metabolism*
  • Humans
  • Oxidative Stress / physiology
  • Pyroptosis / physiology
  • Signal Transduction / physiology
  • Urinary Tract Infections / metabolism
  • Urinary Tract Infections / pathology*
  • Uropathogenic Escherichia coli / metabolism
  • Uropathogenic Escherichia coli / pathogenicity*
  • Virulence / physiology*


  • Hemolysin Proteins

Grants and funding

Financial disclosure This work was partially supported by Natural Science Foundation of Jiangsu Province (BK20191122) (http://kjjh.jspc.org.cn/, to G.H.), the project of Jiangsu Commission of Health (H2019085) (http://wjw.jiangsu.gov.cn/, to G.H.), and National Natural Science Foundation of China Young Scholars Project (31902242) (http://www.nsfc.gov.cn/, to C.W.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.